This proposal will determine the role of mechanical stress and strain in the activation of rapidly adapting (RA) mechanoreceptor neurons. The importance of this project relates to the ubiquity of mechanical sensation and the fact that basic processes in mechanoreception are not well understood. In mechanoreceptors, external stimuli do not act directly on the transducer elements. Rather, stimuli act on some tissue; and internal states in the tissue in turn act on the transducer. This process is not well understood, and it has been suggested that transducer elements may be sensitive to shear stress or strain. RA mechanoreceptors will be studied in isolated skin - nerve preparations from rat hairy skin. Major advantages of RA cutaneous afferents are that they have a very rapid response, and they reside in a viscoelastic tissue. When skin is dynamically stretched, stress and strain are transiently decoupled from each other. The response of cutaneous RAs is fast enough that it can be determined whether neuronal responses are associated with transiently-decoupled stress or strain components. In this proposal we propose to dynamically manipulate shear stress, and measure shear strain, in an attempt to determine whether activation of afferent neurons is caused by shear or normal components of stress or strain.